Field of the Disclosure
The present disclosure pertains to rock climbing and industrial alpinism (steeplejacking) and can be used for rappelling or ascending a climber, as well as for tightening polyspasts.
Description of the Related Art
The best-known apparatus for rappelling is a FIGURE EIGHT (see, for example, Ref. 1) which comprises two rings inseparably connected to each other, one of the rings being 1.5 times smaller than the other, the inner diameter thereof being up to 50 mm.
The FIGURE EIGHT has several deficiencies. During the rappelling, a rope twisting occurs, and it is difficult enough to position the loose end of the rope during stops.
To solve the problem of positioning the loose end, a FIGURE EIGHT with ears is used. This type of FIGURE EIGHT, unlike a conventional one, additionally comprises two ears on the sides of the large ring, the ears being connected to each other and attached to a pin inseparably connected to the large ring. Still, the twisting of the loose end of the rope remains a drawback of the FIGURE EIGHT with ears.
Another known apparatus for rappelling is a Gri-Gri (see, for example, Ref. 2), including a body, which comprises a flywheel, including a cam, the flywheel being connected to a lever. In the Gri-Gri, the rope rounds the circular cam-like flywheel. When loaded, the rope turns the flywheel around its axis, which presses it to the body and thus blocks rappelling. The turning angle of the lever can be used to control the speed of paying out the rope through the apparatus, and to unblock it.
The Gri-Gri apparatus is automatically blocked under a load and does not twist the rope. During the operation, however, a dirty rope can hinder the rappelling, and the rappelling is impossible using two ropes.
Also known in the art is a plurality of modifications of descender apparatuses (see, for example, Ref. 3) that have two pulleys placed into a frame of two plates, one of the plates being rotatable around the axis of one of the pulleys to be able to put in the rope. In a closed position, the rotatable plate is kept in place by a latch.
To increase the safety and comfort of rappelling, descenders are used which, unlike those described above, are equipped with a control and unblocking handle adapted to regulate the force of friction of the rope. Main disadvantages of these descenders include their inability to function with two ropes, the impossibility to remove the rope without using additional clamp, and the impossibility of using them for ascension.
The closest to the present disclosure in technical essence is a clamp (see, for example, Ref. 4), which comprises a hollow all-metal body with free end faces, a partially open base, and one edge, the body having a hole in the upper portions thereof to fix the axis of a clamping element (a cam) with notches. There is a special aperture for a snap-hook in the upper portion of the body, and there is a hole for a foot pedal in the lower portion thereof.
The deficiencies of the prototype involve the impossibility of using it with two ropes, its structural limitations that allow using it only for ascension, as well as the impossibility of controlling the force of friction of the rope.